1. Field of the Invention
The present invention relates to a coated molding comprising a thermoplastic resin composition molding with excellent coating properties including a thermoplastic resin and a compound having a functional group, and a coating layer on the surface of the thermoplastic resin composition molding, and to a production method therefor. The coated molding is suitable for industrial materials such as automobile parts, household electric appliance parts, electrical equipment parts, and other commodities.
2. Description of the Related Art
Thermoplastic resins such as a polypropylene resin are light-weight, and have excellent stiffness, hardness, and heat resistance. Also, they are inexpensive and can be easily molded into a desired shape with various molding methods such as injection molding, calender molding, and extrusion molding. Accordingly, they have been widely used for automotive interiors including instrument panels, trims, and pillars, automotive exteriors including fenders, bumpers, side molding, mud guards, and mirror covers, other automobile parts, household electric appliance parts, industrial parts, and other commodities. However, a polyolefin based resin generally has problems with coating properties, coating film adhesive properties, and adhesive properties with a coating agent, which are required to be improved.
Typically, a polyolefin based resin such as a polypropylene resin are coated after a surface treatment.
The surface treatment prior to coating is for degreasing or polarizing the surface of a non-polar polyolefin based resin molding. Specifically, the non-polar polyolefin based resin is surface-treated with a halogenated hydrocarbon such as trichloroethane, is oxidized or polarized with a corona discharge, a plasma jet and the like, and is then coated.
Another means for providing the coating properties is to add a very low molecular weight ethylene propylene rubber (EPR) to the non-polar polyolefin based resin composition. Japanese Unexamined Patent Application Publication Hei.6-157838 proposes that modified polyolefin with a compound having a polar group is added to the non-polar polyolefin based resin composition. Japanese Unexamined Patent Application Publication Hei.5-39383 proposes that a modified polyolefin with a compound having an unsaturated hydroxyl group is added to a non-polar polyolefin based resin composition. Japanese Unexamined Patent Application Publication Hei.3-157168 proposes that an oligomer having a polar end group is added to a non-polar polyolefin based resin composition.
However, in these methods, a large amount of very low molecular weight EPR or chemically modified compounds are required to provide sufficient coating properties.
An object of the present invention is to provide a coated molding where a firmly adhered coating layer is formed on the surface of a thermoplastic resin composition molding without performing a complex surface treatment.
According to the present invention, a molding of a thermoplastic resin composition may be obtained by adding a compound having a functional group such as an epoxidized diene based block copolymer to a thermoplastic resin such as a polypropylene based resin, a coating layer can be formed with an ultraviolet curable urethane acrylate coating agent, and firmly adhered to the molding without a special surface treatment such as a corona discharge treatment.
According to the first aspect of the present invention, a coated molding comprising a molding (M) of a thermoplastic resin composition (A) including a thermoplastic resin (a1) and a compound (a2) having a functional group, and a coating layer (B) formed on the surface of the molding (M) is provided.
According to the second aspect of the present invention, the compound (a2) has an epoxy group.
According to the third aspect of the present invention, the compound (a2) having the epoxy group is an epoxidized diene based block copolymer obtained by epoxidizing a diene based block copolymer or a partially hydrogentated diene based block copolymer, wherein prior to epoxidizing, the diene based block copolymer or partially hydrogenated diene based block copolymers consists of a polymer block consisting of a vinyl aromatic hydrocarbon compound, and a polymer block consisting of a conjugate diene compound, or a partially hydrogenated conjugate diene compound.
According to the fourth aspect of the present invention, the coating layer (B) is formed by an ultraviolet curable urethane acrylate based coating agent.
According to the fifth aspect of the present invention, the thermoplastic resin composition (A) comprises 85% to 97% by weight of the thermoplastic resin (a1) and 15% to 3% by weight of the compound (a2) having the functional group.
According to the sixth aspect of the present invention, the thermoplastic resin (a1) is a polyolefin based resin.
According to the seventh aspect of the present invention, the polyolefin based resin is a polypropylene based resin and/or a polyethylene based resin.
According to the eighth aspect of the present invention, a method for producing the above-mentioned coated molding comprises the steps of coating a surface of the molding (M) with the coating agent (b), and reacting the compound (a2) with the coating agent (b) to form the coating layer (B) thereon.
According to the ninth aspect of the present invention, the coating agent (b) is coated after the surface of the molding is treated with a hydrophobic solvent.
According to the tenth aspect of the present invention, the hydrophobic solvent is one or more selected from the group consisting of xylene, cyclohexane, and toluene.